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I’m trying to get my feet wet with native plugin programming and my goal is to write a OSX / Mac plugin that can be used for Push notifications on the Mac. So far I’ve followed the basic steps to create a cocoa bundle and created an objective C class named “Plugin” (Plugin.h/.m).

For a simple test I would like to call from Unity a NSLog output in the plugin via the SoundTest method. The .m file looks like this:

#include 
#import "Plugin.h"

@implementation Plugin

- (void)DebugLog:(NSString *)msg {
    NSLog(@"###################################");
}

- (void)SoundTest { // <-------------- WANT TO CALL THIS ONE FROM C# CODE
    NSLog(@"======================================");
}
...
...

I created a corresponding C# file to import the plugin:

using UnityEngine;
using System.Collections;
using System;
using System.Runtime.InteropServices;

public class PushNotificationPlugin {

	//Calls to the native plugin
	[DllImport ("PushNotification")]
	public static extern void SoundTest();

Now I got in Xcode a pre-defined PCH file and I read that I have to define in there via some extern “C” the method call. But how?

This is the generated PushNotification-Prefix.pch file:

#ifdef __OBJC__
    #import 

extern "C" {
   static extern void SoundTest(); // <----- doesn't work
}  

#endif
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Hey Martin,

you cannot call Obj-C code directly from C#. The line:

 static extern void SoundTest();

declares a C prototype for a function SoundTest(), but your code does not actually define such a function, so it cannot be found. The Obj-C method you have is not a C function and won’t match that prototype. In your case, I don’t see a reason to write SoundTest as an Obj-C method at all, just make it a normal C function:

void SoundTest() { // <-------------- WANT TO CALL THIS ONE FROM C# CODE
    NSLog(@"======================================");
}

Lastly, make sure you are compiling with the correct architecture (Unity 4.1 will only load 32-bit plugins, but latest versions of Xcode default to building 64 bit binaries).